Micros to Have in Mind When Endurance Training

Do athletes need more micronutrients? 

The daily requirement for some vitamins and minerals might be increased for highly physically active people (1). When training regularly, there is an increased need for energy intake (providing energy balance’ is the goal). This means that with a well-balanced diet, meeting your energy requirements sees your micro intake increase automatically. It’s usually not a problem to get enough micros if you’re promoting energy balance and have a varied diet that includes all food groups (2).

Endurance training puts higher demands on the body. If you’re excluding things from your diet (preferences or allergies) you need to replace them with equal nutrients from other healthful sources. The more you exclude, the more you need to be aware of. If you have a restrictive diet, suspect you have some kind of deficiency, or you’re looking to lose weight (operating on a large energy deficit) always consult a dietitian or nutritionist.

Vitamins

Vitamins are organic substances that help your body function normally. We get vitamins through food, since the body can’t produce them on its own, or doesn’t produce enough of them itself (Vitamin D is a rare exception, since it’s formed in the skin through sunlight). Vitamins are usually divided into fat-soluble and water-soluble vitamins. The main difference between them is how they are metabolized and stored in the body (3).

Water soluble vitamins:

These vitamins respond quickly to nutrition intake and, if over-consumed, leave the body through your urine. These vitamins aren’t stored, and should therefore preferably be included in your daily diet. This group includes vitamin B6, vitamin B12, vitamin C, biotin, folate, niacin, pathogenic acid, riboflavin, and thiamine. Many vitamins, particularly the water-soluble vitamins, are involved in mitochondrial energy metabolism.They are therefore of great importance when doing endurance training (4).

Fat soluble vitamins: 

The fat-soluble vitamins require the presence of fat in order to be taken up and stored – one of the reasons why it’s important to include the right amount of healthy fats in your diet. Because we stockpile them, intake of them isn’t as important as intake for water-soluble vitamins. Storing them also means we can get too much of them (this is nothing to worry about from only a dietary intake, but supplements should be taken with caution). The fat-soluble vitamins are A, D, E and K (4).

Vitamin D: One of the fat-soluble vitamins to keep in mind. The lowest levels of vitamin D are seen in athletes who train a lot inside, since the sun is the main source of the vitamin.  The vitamin regulates calcium balance in bones and teeth – it is very important for our bone health. Since the sun is our best source of this vitamin, it means that if you live somewhere with limited sunlight during winter months, your intake might be low that around that time of year. Sources that should be included in your diet are, for example, oily fish such as salmon, eggs and enriched products. You might also need supplements during those dark winter months (5)

Minerals

Lack of minerals can cause specific disease symptoms, and large amounts can be harmful. Through eating, we usually don’t exceed our daily recommendations, but supplements should be taken with caution, just as for the fat-soluble vitamins (4).

Some of the important minerals to keep in mind when working out:

Zinc: Vital for a lot of body processes, Zinc is especially important for our metabolism and immune system. Sources: meat, shellfish, dairy products, nuts and whole grains (6).

Magnesium: A mineral that contributes to both normal muscle and nervous system functions. Sources: legumes, leafy vegetables, whole grains, meat, fish and shellfish (6).

Iron: A trace mineral that is associated with numerous processes important for working out, such as transporting oxygen in the body. Menstruating women and adolescents have an increased risk of depleting their iron stores. High-intensity and endurance training on hard surfaces also leads to increased breakdown of red blood cells (hemolysis) = which can lead to an increased need for iron (7).

There are two forms of dietary iron, heme iron and non heme iron. Heme iron is found in animal sources: intestinal and blood foods such as liver and blood pudding, meat, eggs and seafood. Non heme iron is found in vegetable sources such as: seeds, nuts and green leafy vegetables and iron-fortified breakfast cereals. Heme iron has a higher bioavailability – meaning it is easier for the body to absorb, while non heme iron has a lower bioavailability, which means that we don’t absorb it at the same rate from our food (6).

There are inhibitory and stimulating factors that can affect the absorption of iron. Vitamin C and muscle meat in a meal enhance iron absorption. While phytates (found in i.e. legumes and grains) calcium and polyphenols (i.e. found in tea and coffee) inhibit the absorption. 

Thus if you’re doing endurance training and on a plant-based diet, it can be beneficial to have the enhanced and inhibitor factors in mind. Have an orange (vitamin C) after or with your meal since it enhances the iron uptake. Additionally, make sure to include vegetable iron sources in all meals to prevent a shortage. If you suspect that you have iron deficiency, always consult your healthcare provider (6).

Antioxidants 

These are substances that, in various ways, provide protection from and take care of the excess of free radicals. Free radicals are substances that can have harmful effects on the body (so-called oxidative stress). When we work out, we have higher oxygenation and expose the body to a kind of “stress” which therefore results in increased formation of free radicals. It is therefore likely that the need for antioxidants would be increased when training hard. Several nutrients act as antioxidants, such as vitamin E, vitamin C, riboflavin and carotenoids. Many other substances in food can act as antioxidants (called bioactive substances). Examples of these are flavonoids and anthocyanins (8).

Colorful foods are loaded with antioxidants and many other nutrients. There are great reasons to always strive for a colorful plate! 
Antioxidant rich food to include in your daily diet: Berries (all kinds), onions, various cabbage, coca (dark chocolate) green tea, beets, grapes, oranges, nuts and seeds.

References

1. Andersson, A. Idrottsnutrition. I Näringslära för högskolan, Abrahamsson, L., Andersson, A., Nilsson, G (red.), 410-439. Stockholm: Liber AB, 2013.
2. Sveriges Olympiska Kommitté/SOK. Kostrekommendationer för olympiska idrottare. 2016. https://sok.se/download/18.3e3b95e91555e5c9d8b6a15e/1466669159954/Kostrekommendationer+för+Olympiska+Idrottare_Version+hemsidan_juni2016.pdf 
3. Livsmedelsverket. Vitaminer och antioxidanter. 2019. https://www.livsmedelsverket.se/livsmedel-och-innehall/naringsamne/vitaminer-och-antioxidanter (Hämtad 2019-09-13).
4. Ellegård, L., Rothenberg, E., Nilsson, G. Vitaminer och övriga bioaktiva ämnen. I Näringslära för högskolan, Abrahamsson, L., Andersson, A., Nilsson, G (red.), 223-278. Stockholm: Liber AB, 2013.
5. Burke, L., Deakin, V. Clinical Sports Nutrition. 5th ed. New York: Mc Graw Hill Education, 2015, 251.
6. Becker, W. Mineralämnen. I Näringslära för högskolan, Abrahamsson, L., Andersson, A., Nilsson, G (red.),180-222. Stockholm: Liber AB, 2013.
7. Burke, L., Deakin, V. Clinical Sports Nutrition. 5th ed. New York: Mc Graw Hill Education, 2015, 293.
8. Livsmedelsverket. Antioxidanter. 2019. https://www.livsmedelsverket.se/livsmedel-och-innehall/naringsamne/vitaminer-och-antioxidanter/antioxidanter/ (Hämtad 2019-09-13).